docs: def minus(a, b):
      '''
      minus(a, b) returns the difference a - b as a numpy array object. Unlike numpy's subtract
        function or a - b syntax, minus will thread over the earliest dimension possible; thus if
        a.shape is (4,2) and b.shape is 4, a - b is a equivalent to [ai-bi for (ai,bi) in zip(a,b)].
      '''
      (a,b) = unbroadcast(a,b)
      return a - b